He said in a letter to the Group of 20 leaders that they account for 85 percent of the world's gross domestic product and have "a direct interest and critical role to play in helping developing countries cope with the crisis."

"Let us remember that we are only as strong as the weakest health system in our interconnected world," the U.N. chief said. "We must create the conditions and mobilize the resources necessary to ensure that developing countries have equal opportunities to respond to this crisis in their communities and economies."

Guterres warned: "Anything short of this commitment would lead to a pandemic of apocalyptic proportions affecting us all."

U.N. spokesman Stephane Dujarric said G20 leaders are expected to hold a virtual summit meeting Thursday.

Guterres, who will participate in the meeting, said COVID-19 is a human crisis with many threats, noting that even in the wealthiest countries "we see health systems buckling under pressure."

"Around the world, the socioeconomic impacts of the pandemic are already tangible — schools are closing, already pervasive inequalities are deepening, many countries are unable to respond to the enormous needs of the elderly," he said. "And women, who represent 70 per cent of health care workers, are disproportionately affected."

"A recession is in prospect. The question is: how long it will last and how much damage will it do to the productive capacities of our economies and the livelihoods of our citizens," Guterres said.

By the end of the year, the secretary-general said "the cost of this pandemic is likely to be measured in the trillions of dollars" and that's why the G20 leaders "must inject massive resources into economies, reaching double digit percentage points in the world's gross domestic product."

He said a coordinated stimulus package in the trillions of dollars "would include scaling up cash transfer measures, social protection, tax abatement, fiscal stimulus, low interest rates, access to credit, insurance and wage support schemes."

The secretary-general stressed that "these expansionary policies must be accompanied by a clear repudiation of protectionism."

"I urge G-20 leaders to commit to ban tariffs, quotas or non-tariff measures, and remove restrictions on cross-border trade that affect the deployment of medical equipment, medicines and other essential goods to fight the epidemic," Guterres said.

He also encouraged countries to waive sanctions to allow delivery of food, health supplies, medical equipment and support for the COVID-19 crisis, saying: "This is the time for solidarity not exclusion."

Guterres also called on the G20 leaders to establish a coordinated response to suppress the coronavirus everywhere, guided by the U.N. World Health Organization,.

He said this would provide countries with strong capabilities to stop transmission of COVID-19 including testing, tracing, quarantining, treating the sick, coordinating measures to restrict movements and contacts and coordinating scientific collaboration in the search for a vaccine and treatments.

Guterres said the U.N. supply network is at the G20's disposal to help procure medical and protective equipment and establish transport and supply chains.

He also stressed the responsibility of all nations to "recover better" from the pandemic and ensure that future development programs contribute to preserving the environment and addressing climate change.